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Microbial degradation of organic matter is a key driver of subsurface biogeochemistry. Here, we present a bioenergetics-informed kinetic model for the anaerobic degradation of macromolecular organic matter that accounts for extracellular hydrolysis, fermentation, and respiration. The catabolic energy generated by fermentation and respiration is allocated to biomass growth, production of extracellular hydrolytic enzymes, and cellular maintenance. Microbial cells are assumed to exist in active or dormant states with marked differences in maintenance energy requirements. Dormant cells are further assumed to fulfill their maintenance energy requirements by utilizing their own biomass instead of relying on external substrates. When the catabolic Gibbs energy production for a given functional group of microorganisms exceeds the total maintenance energy requirement of the active cells, biomass growth, re-activation of dormant cells, and production of extracellular hydrolytic enzymes are possible. The latter, in turn, allows the microbial community to access more of the available external organic substrates. In the opposite case, active cells decay or become dormant. We apply the model to simulate the anaerobic degradation of cellulose by a hypothetical microbial community consisting of cellulolytic fermenting bacteria and sulfate-reducing bacteria, under conditions representative of those encountered in water-saturated subsurface environments.

A systematic and structure-agnostic method for identifying heterogeneous activity of solid acids for catalyzing cellulose hydrolysis is presented. The basis of the method is preparation of a supernatant liquid by exposing the solid acid to reaction conditions and subsequent use of the supernatant liquid as a cellulose hydrolysis catalyst to determine the effects of in situ generated homogeneous acid species. The method was applied to representative solid acid catalysts, including polymer-based, carbonaceous, inorganic, and bifunctional materials. In all cases, supernatant liquids produced from these catalysts exhibited catalytic activity for cellulose hydrolysis. Direct comparison of the activity of the solid acid catalysts and their supernatants could not provide unambiguous detection of heterogeneous catalysis. A reaction pathway kinetic model was used to evaluate potential false-negative interpretation of the supernatant liquid test and to differentiate heterogeneous from homogeneous effects on cellulose hydrolysis. Lastly, differences in the supernatant liquids obtained in the presence and absence of cellulose were evaluated to understand possibility of false-positive interpretation, using structural evidence from the used catalysts to gain a fresh understanding of reactant–catalyst interactions. While many solid acid catalysts have been proposed for cellulose hydrolysis, to our knowledge, this is the first effort to attempt to differentiate the effects of heterogeneous and homogeneous activities. The resulting supernatant liquid method should be used in all future attempts to design and develop solid acids for cellulose hydrolysis.

11 figures, 4 tables.-- Supplementary information available.-- © 2021. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/, Carbon nanostructures have attracted a long-lasting interest in cellulose hydrolysis reaction. Herein, the usefulness of catalyst downsizing is addressed using various graphene oxide (GO) morphologies, including nanofibers (GONF), sheets of few-layers (FLGO) and quantum dots (GOQD). Such materials were obtained from carbon nanofibers by oxidative cutting and subsequent exfoliation and fractioning in size. The synthesis process incorporated numerous active species (S- and O- functional groups) onto the carbon sp2-network, whose relative abundance was in some instances tuned by hydrothermal reduction. Chemical and structural analysis of GO materials was performed by XRD, TEM, XPS and elemental analysis. GOQDs, as the smallest particle size GO material, exhibited the highest catalytic activity. However, its behaviour was dependent on the crystalline features of the starting cellulose and the substrate-catalysts interaction degree. Thus, only 17.8% of raw cellulose was depolymerized into sugars after 24 h at 135 °C, which rose to 60.1% upon enhancing its reactivity by ball-milling (8h, 600 rpm). A simple mix-milling of the cellulose with the catalyst for 10 min enabled an effective solid-solid contact, affording complete conversion and 83.5% of glucose. In comparison, 71.3% and 60.4% of glucose was obtained from their sister counterparts: FLGO and GONF, respectively., Authors are grateful for the financial support from FEDER and the Spanish Ministry of Economy and Competitiveness (Project ENE2017-83854-R). The microscopy works have been conducted in the Advanced Microscopy Laboratories (LMA) at Institute of Nanoscience of Aragón (INA). We would like to thank the LMA-INA for offering access to their instruments and expertise. Also, the assistance of Servicio General de Apoyo a la Investigación-SAI (University of Zaragoza) is acknowledged.

Solid acids as heterogeneous catalysts for cellulose hydrolysis have drawn increasing attention; however, current solid acids face challenges such as high catalyst loading (low catalytic activity),...

Pretreatment can improve the hydrolysis efficiency of cellulose, in which biological pretreatment plays an important role. In the present study, we uncovered that Rhodococcus has the ability of lig...

In recent years, research activities involved in the production of nanocellulosic materials have grown substantially, rapidly stimulating the development of innovative production techniques. These materials are chemically extracted by acid-catalyzed Hydrolysis of the renewable and widely available cellulosic biomass. In this regard, sulfuric acid-catalyzed Hydrolysis of cellulosic biomass is a commonly known method for the production of nanostructured cellulose. However, this method may result in many disadvantages, including short catalyst-lifetime, corrosive to the reactor materials and managing the spent sulfuric acid resulted from the production process. This dictates the implementation of an eco-industrial alternative for the catalytic production of nanocrystalline cellulose (NCC). A viable and practical alternative is the application of heterogeneous (solid acids) catalysts, which can be more conducive in providing favorable platforms for efficient cellulose hydrolysis. This review highlights the current production methods of nanocrystalline cellulose. Further, recent literature on the heterogeneous-catalytic conversion of cellulosic biomass is briefly discussed. The limitations and disadvantages of these techniques are also described.

Enzymatic catalysis on the insoluble substrates commonly suffers from low enzyme stability, catalytic activity, and product recovery. Herein, a "thermal cycling method" of DNA material is proposed to tackle the challenges in enzymatic reaction, in which a thermal responsive self-assembled DNA material is designed for enzyme recovery. We demonstrate the remarkable advantages of this new method in cellulosic hydrolysis. The responsive DNA material has a solution to gel transition temperature at 13 °C. Therefore, the cellulase (CEL) can be on-demand switched between the mobile state, enabling high reactivity, and fixed state, facilitating CEL recovery and reuse. As a result, this system showed good catalytic activity and operational stability even at extremely high cellulose concentrations (100 mg/mL). We believe that this new strategy provides a general platform not only for enzymatic reactions but also for other bioderived reactions.

The plantain agro-industry generates different residues in the harvest and post-harvest stages. Therefore, the design of processes for valorization is required. The aim of this work was to design and techno-economically evaluate the processes for the production of single-cell protein, natural fibers, and biomethane from plantain residues by process simulation in the framework of the design of a future biorefinery for valorization of these residues. The processes were simulated using SuperPro Designer. The scale size was calculated at 1,267,071 tons for the processing of plantain lignocellulosic waste (pseudostems) and 3179 tons for the processing of starchy waste (rejected unripe plantain fruits). The results obtained suggest that the best alternative for the valorization of plantain residues corresponded to the production of natural fibers, with a net present value of $29,299,000. This work shows that waste from the plantain agro-industry exhibits high potential as a feedstock for the production of value-added products. In addition, the process flowsheets simulated in this work can be integrated into the basic design of a biorefinery processing plantain waste., This work was supported by the Colombian Ministry for Science, Technology, and Innovation (MinCiencias) through the research project “Design of a Biorefinery for the Use of the Lignocellulosic and Starchy Waste of the Plantain Agribusiness” (Call 757 for Funding of National Doctorates) [grant 1640318]; and the Universidad de Caldas through the research project “Basic Process Development for the Use of Agro-industrial and Urban Waste Under the Concept of Biorefineries” [grant 0240518]., info:eu-repo/semantics/publishedVersion

Commercial cellulase Cellic CTec2 was immobilized by the entrapment technique in sol–gel matrices, and sol–gel entrapment with deposition onto magnetic nanoparticles, using binary or ternary systems of silane precursors with alkyl- or aryl-trimethoxysilanes, at different molar ratios. Appropriate tailoring of the sol–gel matrix allowed for the enhancement of the catalytic efficiency of the cellulase biocatalyst, which was then evaluated in the hydrolysis reaction of Avicel microcrystalline cellulose. A correlation between the catalytic activity with the properties of the sol–gel matrix of the nanobiocatalysts was observed using several characterization methods: scanning electron microscopy (SEM), fluorescence microscopy (FM), Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA/DTA). The homogeneous distribution of the enzymes in the sol–gel matrix and the mass loss profile as a function of temperature were highlighted. The influence of temperature and pH of the reaction medium on the catalytic performance of the nanobiocatalysts as well as the operational stability under optimized reaction conditions were also investigated; the immobilized biocatalysts proved their superiority in comparison to the native cellulase. The magnetic cellulase biocatalyst with the highest efficiency was reused in seven successive batch hydrolysis cycles of microcrystalline cellulose with remanent activity values that were over 40%, thus we obtained promising results for scaling-up the process.

Actinobacteria form the largest phylum consisting of diverse, ecologically unique and biologically active members. The actinobacteria are omnipresent and occur in various habitats such as cold environment, aquatic, desert and terrestrial ecosystems. Though the studies are available on actinobacteria at various habitats very few reports are available on cold tolerant/loving actinobacteria in the Southern Ocean part of the Antarctic Ocean. In this context, the present work was designed to isolate and characterize the actinobacteria in the Polar Front region of the Southern Ocean waters and species of Nocardiopsis and Streptomyces were identified. Among those, the psychrophilic actinobacterium, Nocardiopsis dassonvillei PSY13 was found to have good cellulolytic activity and it was further studied for the production and characterization of cold-active cellulase enzyme. The latter was found to have a specific activity of 6.36 U/mg and a molar mass of 48 kDa with a 22.9-fold purification and 5% recovery at an optimum pH of 7.5 and a temperature of 10 ºC. Given the importance of psychrophilic actinobacteria N. dassonvillei PSY13 can be further exploited for its benefits, meaning that the Southern Ocean harbours biotechnologically important microorganisms that can be further explored for versatile biotechnological and industrial applications.

Glucose produced by catalytic hydrolysis of cellulose is an important platform molecule for producing a variety of potential biobased fuels and chemicals. Catalysts such as mineral acids and enzymes have been intensively studied for cellulose hydrolysis. However, mineral acids show serious limitations concerning equipment corrosion, wastewater treatment and recyclability while enzymes have the issues such as high cost and thermal stability. Alternatively, solid acid catalysts are receiving increasing attention due to their high potential to overcome the limitations caused by conventional mineral acid catalysts but the slow mass transfer between the solid acid catalysts and cellulose as well as the absence of ideal binding sites on the surface of the solid acid catalysts are the key barriers to efficient cellulose hydrolysis. To bridge the gap, bio-inspired or bio-mimetic solid acid catalysts bearing both catalytic and binding sites are considered futuristic materials that possess added advantages over conventional solid catalysts, given their better substrate adsorption, high-temperature stability and easy recyclability. In this review, cellulase-mimetic solid acid catalysts featuring intrinsic structural characteristics such as binding and catalytic domains of cellulase are reviewed. The mechanism of cellulase-catalyzed cellulose hydrolysis, design of cellulase-mimetic catalysts, and the issues related to these cellulase-mimetic catalysts are critically discussed. Some potential research directions for designing more efficient catalysts for cellulose hydrolysis are proposed. We expect that this review can provide insights into the design and preparation of efficient bioinspired cellulase-mimetic catalysts for cellulose hydrolysis.

The hydrolysis of cellulose by processive cellulases, such as exocellulase TrCel7A from Trichoderma reesei, is typically characterized by an initial burst of high activity followed by a slowdown, often leading to incomplete hydrolysis of the substrate. The origins of these limitations to cellulose hydrolysis are not yet fully understood. Here, we propose a new model for the initial phase of cellulose hydrolysis by processive cellulases, incorporating a bound but inactive enzyme state. The model, based on ordinary differential equations, accurately reproduces the activity burst and the subsequent slowdown of the cellulose hydrolysis and describes the experimental data equally well or better than the previously suggested model. We also derive steady‐state expressions that can be used to describe the pseudo‐steady state reached after the initial activity burst. Importantly, we show that the new model predicts the existence of an optimal enzyme‐substrate affinity at which the pseudo‐steady state hydrolysis rate is maximized. The model further allows the calculation of glucose production rate from the first cut in the processive run and reproduces the second activity burst commonly observed upon new enzyme addition. These results are expected to be applicable also to other processive enzymes.

Sulfonated carbonaceous solid acids are key heterogeneous catalysts and are widely used in acid-catalyzed reactions, especially in biomass transformation. In this work, the sulfonated carbonaceous solid acids were prepared and their stability was examined in cellulose hydrolysis at 170 °C. Their activity decreased largely after the hydrothermal treatment at 170 °C, as a result of the leaching of their SO3H species. Characterizations of the filtrates after the hydrothermal treatment of these solid acid catalysts by NMR and laser scattering demonstrated that the leaching of SO3H sites was not caused by the cleavage of C S bonds, but by the exfoliation of colloidal carbon particles with SO3H sites from the catalysts. Such leaching problem led to significant decrease in SO3H density for the carbon-based solid acids that synthesized by traditional sulfonation methods because of their uneven distribution of SO3H sites. To address this issue, carbon precursors with more free C H sites were applied to regulate the distribution of SO3H sites. As a consequence, the evenly distributed SO3H sites resulted in less change in acid density after the hydrothermal treatment, and maintenance of high SO3H density. This study could provide new guidance to further design of water-tolerant solid acid catalysts, and would promote the development of energetically efficient processes to convert cellulose.

In comparison with templates of zeolites and silica, a template of nano-magnesium oxide (nano-MgO) has some unique advantages. Namely, it is easily removed by dilute noncorrosive acid solution, is recyclable for nano-MgO precursors, and has tunable pore size by selecting various nano-MgO precursors. In this study, the nano-MgO as a hard template synthesis of lignin carbon-based solid acids catalyst was characterized by scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) spectroscopy, and X-ray diffraction (XRD). After using nano-MgO as a hard template, the resulting nano-MgO mesoporous carbon-based solid acids (MLCSAs) presented a uniform porous morphology and the smooth surface became rough. When the carbonization temperature was 400°C, the catalytic activity of MLCSAs for the hydrolytic reaction of cellulose was greater than lignin carbon-based solid acids (LCSAs) without nano-MgO as a hard template.

High-value utilization of cellulosic biomasses via the most promising enzymatic method is the key to solve a series of global strategic issues but its industrialization was seriously hindered by the high cost. Immobilization of enzyme to realize its recycling is one solution; however, how to capture and hydrolyze the insoluble cellulose effectively via the immobilization system remains challenging. Herein, inspired by the predation process of the sea anemone, a cost-effective biomimetic cellulase-loaded enzymatic film was constructed. The cellulase loaded on the film can adjust its spatial orientation freely, thus their catalytic centres can easily reach the surface of the cellulose to perform the “predation” process effectively. As a result, this immobilization system can largely increase the efficiency of the insoluble cellulose hydrolysis and can be recycled for at least 8 cycles without activities loss. Therefore, it can largely reduce the cost of the cellulose conversion in the industrial areas.

In several industries such as food, paper and pulp, and textiles as well as purifying the digestibility of preservatives and animal feeds in cleaners, microbial cellulases are increasingly being used for a widespread variety of industrial purposes. Further advancement in cellulase performance requires the enhanced involvement of substrate features, molecular structure, and cellulase function, together with the concerned mechanisms of the hydrolysis of microbial cellulose. CBP adopts the one-pot fermentations of pentose and hexose, cellulase production, and cellulose hydrolysis. This chapter focuses on several approaches and optimizing parameters for low cost, easy synthesis, and the conversion of lignocellulosic biomass cellulase materials and the biodegradable production of microbial cellulase. This chapter also focuses on the various requests for bacterial cellulase in several industries and their future prospectives.

Intermediate-level radioactive waste includes cellulosic materials, which under the hyperalkaline conditions expected in a cementitious geological disposal facility (GDF) will undergo abiotic hydrolysis forming a variety of soluble organic species. Isosaccharinic acid (ISA) is a notable hydrolysis product, being a strong metal complexant that may enhance the transport of radionuclides to the biosphere. This study showed that irradiation with 1 MGy of γ-radiation under hyperalkaline conditions enhanced the rate of ISA production from the alkali hydrolysis of cellulose, indicating that radionuclide mobilisation to the biosphere may occur faster than previously anticipated. However, irradiation also made the cellulose fibres more available for microbial degradation and fermentation of the degradation products, producing acidity that inhibited ISA production via alkali hydrolysis. The production of hydrogen gas as a fermentation product was noted, and this was associated with a substantial increase in the relative abundance of hydrogen-oxidising bacteria. Taken together, these results expand our conceptual understanding of the mechanisms involved in ISA production, accumulation and biodegradation in a biogeochemically active cementitious GDF., Microbial degradation of irradiated cellulose can mitigate the ISA-enhanced radionuclide transport from a cementitious geological disposal facility to the biosphere.

International audience; the aim of this work was to demonstrate the feasibility of second-generation bioethanol production using for the first time a sawmill mixed feedstock comprising four softwood species, representative of biomass resource in auvergne-rhone-alpes region (france). the feedstock was subjected to a microwave-assisted water/ethanol organosolv pretreatment. the investigation focused on enzymatic hydrolysis of this pretreated sawmill feedstock (psf) using cellic® ctec2 as the enzyme, followed by fermentation of the resulting sugar solution using saccharomyces cerevisiae strain. the cellulose-rich psf with 71% w/w cellulose content presented high saccharification yields (up to 80%), which made it perfect for subsequent fermentation; this yield was predicted vs. time up to 5.2% w/v psf loading using a mathematical model fitted only on data at 1.5%. finally, high psf loading (7.5%) and scaleup were shown to impair the saccharification yield, but alcoholic fermentation could still be carried out up to 80% of the theoretical glucose-to-ethanol conversion yield.

Cellulose saccharification to glucose is an operation of paramount importance in the bioenergy sector and the chemical and food industries, while glucose is a critical platform chemical in the integrated biorefinery. Among the cellulose degrading enzymes, β-glucosidases are responsible for cellobiose hydrolysis, the final step in cellulose saccharification, which is usually the critical bottleneck for the whole cellulose saccharification process. The design of very active and stable β-glucosidase-based biocatalysts is a key strategy to implement an efficient saccharification process. Enzyme immobilization and reaction engineering are two fundamental tools for its understanding and implementation. Here, we have designed an immobilized-stabilized solid-supported β-glucosidase based on the glyoxyl immobilization chemistry applied in porous solid particles. The biocatalyst was stable at operational temperature and highly active, which allowed us to implement 25 °C as working temperature with a catalyst productivity of 109 mmol/min/gsupport. Cellobiose degradation was implemented in discontinuous stirred tank reactors, following which a simplified kinetic model was applied to assess the process limitations due to substrate and product inhibition. Finally, the reactive process was driven in a continuous flow fixed-bed reactor, achieving reaction intensification under mild operation conditions, reaching full cellobiose conversion of 34 g/L in a reaction time span of 20 min.

BACKGOUND: To date, it has been challenging to determine the optimal proportions of the individual cellulases in crude extracts and multienzyme systems to promote enzyme synergism. The application of single surface-display of enzymes may obviate such challenges. This article presents a proof of concept of the optimal mixing of single surface-displayed cellulases for cellulose hydrolysis using Simplex lattice mixture design. RESULTS: The recently discovered maximized autotransporter-mediated expression system was used to express the three cellulases. The biochemical screening analysis revealed that the enzymes have a broad range of functional pH (4–9) and temperature (30–100 ∘C) characteristics. The evaluated optima were pH 6 and 60 ∘C. Through the statistical design of experiment, a blend ratio of 1: 1.6: 1.4 of endoglucanase: exoglucanase

This work presents a detailed structure–activity analysis of a polymeric solid acid catalyst used in cellulose hydrolysis. In contrast to previous work, our studies show that the high catalytic act...

Background: Cellulolytic enzymes of microbial origin have great industrial importance because of their wide application in various industrial sectors. Fungi are considered the most efficient producers of these enzymes. Bioprospecting survey to identify fungal sources of biomass-hydrolyzing enzymes from a high-diversity environment is an important approach to discover interesting strains for bioprocess uses. In this study, we evaluated the production of endoglucanase (CMCase) and β-glucosidase, enzymes from the lignocellulolytic complex, produced by a native fungus. Penicillium sp. LMI01 was isolated from decaying plant material in the Amazon region, and its performance was compared with that of the standard isolate Trichoderma reesei QM9414 under submerged fermentation conditions. Results: The effectiveness of LMI01 was similar to that of QM9414 in volumetric enzyme activity (U/mL); however, the specific enzyme activity (U/mg) of the former was higher, corresponding to 24.170 U/mg of CMCase and 1.345 U/mg of β-glucosidase. The enzymes produced by LMI01 had the following physicochemical properties: CMCase activity was optimal at pH 4.2 and the β-glucosidase activity was optimal at pH 6.0. Both CMCase and β-glucosidase had an optimum temperature at 60°C and were thermostable between 50 and 60°C. The electrophoretic profile of the proteins secreted by LMI01 indicated that this isolate produced at least two enzymes with CMCase activity, with approximate molecular masses of 50 and 35 kDa, and β-glucosidases with molecular masses between 70 and 100 kDa. Conclusions: The effectiveness and characteristics of these enzymes indicate that LMI01 can be an alternative for the hydrolysis of lignocellulosic materials and should be tested in commercial formulations.

BACKGROUNDThis study elaborates the possibility to apply combined ionic liquid (IL) and enzyme treatments for pulp fibre modification. The approach involves swelling of fibre surfaces with IL followed by enzymatic modification of the disrupted fibre surface using carbohydrate active enzymes. RESULTSThe capacity of seven cellulose-dissolving or cellulose-swelling ionic liquids to swell pulp fibres was compared. In addition, thirteen cellulases and five xylanases were screened for their IL tolerance, which determines their applicability in combined or sequential IL-enzyme treatments of fibres. Among the studied ionic liquids, 1-ethyl-3-methylimidazolium dimethylphosphate ([EMIM]DMP) and 1,3-dimethylimidazolium dimethylphosphate ([DMIM]DMP) had the strongest effect on fibre swelling. These solvents were also found to be the least inactivating for the studied enzymes. CONCLUSIONEnzyme compatibility and cellulose-dissolving capability are not two conflicting properties of an ionic liquid. (c) 2017 Society of Chemical Industry

Pretreatment and hydrolysis of lignocellulosic biomass are affected by several uncertainties, which must be systematically considered for a robust process design. In this work, stochastic simulations for expected uncertainties in feedstock composition, kinetic parameter values, and operational parameter values for these two steps were performed. The results indicated that these uncertainties significantly impacted the concentration profiles, which could also affect the optimal batch time. Global sensitivity analysis was then used to identify the critical uncertain parameters. In the feedstock components, cellulose and xylan fractions for acid pretreatment and cellulose fraction for enzymatic hydrolysis were important. Temperature was the most sensitive operating parameter for both acid pretreatment and hydrolysis. The activation energies for different reactions were ranked in terms of their impact on process output. The selected parameters were used to develop stochastic process models using Ito process and mean reverting process for feed composition and kinetic parameter uncertainty. (C) 2017 Elsevier Ltd. All rights reserved.

Commercial microcrystalline cellulose (MCC) was pretreated by hydrogenolysis, followed by solvated electron-assisted hydrolysis in Na/liquid NH3 medium. The reducing sugar (RS) yield achieved was 9...

Chemical characterization of cassava stems from different origin revealed that glucans accounted for 54-63% of the dry weight, whereas 35-67% of these glucans consisted of starch. The cassava stems were subjected to a saccharification study including starch hydrolysis, pretreatment with either sulfuric acid or 1-ethyl-3-methylimidazolium acetate ([Emim]OAc), and enzymatic hydrolysis of cellulose. Starch hydrolysis prior to pretreatment decreased sugar degradation, improved enzymatic convertibility of cellulose, and increased overall glucan conversion. Glucan recovery after pretreatment of starch-free cassava stems (SFCS) was around 85%, but below 52% when the stems were pretreated under the same conditions without preparatory starch hydrolysis. The total amount of hydrolyzed glucan after cellulose hydrolysis was two-fold higher for pretreated SFCS than for directly pretreated stems. Pretreatment with [Emim]OAc resulted in 20% higher glucan conversion than pretreatment with acid. Pyrolysis-GC/MS, X-ray diffraction, CP/MAS C-13 NMR and FTIR analyses revealed major differences between H2SO4- and [Emim]OAc-pretreated material. Bio4Energy

Herein, we reported a novel plasma-sulfonation process for carbon materials in dilute sulfuric acid within a few tens of minutes. The total acidic and –SO3H densities of the sulfonated carbon were 4.4 mmol g−1 and 2.2 mmol g−1, respectively. The glucose selectivity during cellulose hydrolysis using a sulfonated carbon catalyst was 83.9% and retained 98% of its performance after recycling.

En la Presente tesis doctoral se ha estudiado el proceso de hidrólisis de celulosa V Uiomása vegetal en agua supercritica. Se ha estudiado la cinética de hidrólisis de celulosa y sus productos derivados, Un intensivo estudio sobre la dependencia de las cineticas con la presion y temperatura fue desarrollado. La produccion de compuestos de alto valor añadido como ácido láctico o glicolaldehido fue analizado utilizando agua supercritica como medio de reaccion e hidróxido de sodio como medio de reaccion. El reactor diseñado y construido para el estudio de la hidrólisis en agua supecritica fue probado con salvado le trigo, como ejemplo de biomasa natural. Además, se ha estudiado teoricamnete la integracion energetica del proceso de hidrólisis de celulosa en agua supercrita con los procesos comerciales de produccion combinada de calor y potencia., Departamento de Ingeniería Química y Tecnología del Medio Ambiente

Background Enzymatic hydrolysis is a major step for cellulosic ethanol production. A thorough understanding of enzymatic hydrolysis is necessary to help design optimal conditions and economical systems. The original HCH-1 (Holtzapple–Caram–Humphrey–1) model is a generalized mechanistic model for enzymatic cellulose hydrolysis, but was previously applied only to the initial rates. In this study, the original HCH-1 model was modified to describe integrated enzymatic cellulose hydrolysis. The relationships between parameters in the HCH-1 model and substrate conversion were investigated. Literature models for long-term (> 48 h) enzymatic hydrolysis were summarized and compared to the modified HCH-1 model. Results A modified HCH-1 model was developed for long-term (> 48 h) enzymatic cellulose hydrolysis. This modified HCH-1 model includes the following additional considerations: (1) relationships between coefficients and substrate conversion, and (2) enzyme stability. Parameter estimation was performed with 10-day experimental data using α-cellulose as substrate. The developed model satisfactorily describes integrated cellulose hydrolysis data taken with various reaction conditions (initial substrate concentration, initial product concentration, enzyme loading, time). Mechanistic (and semi-mechanistic) literature models for long-term enzymatic hydrolysis were compared with the modified HCH-1 model and evaluated by the corrected version of the Akaike information criterion. Comparison results show that the modified HCH-1 model provides the best fit for enzymatic cellulose hydrolysis. Conclusions The HCH-1 model was modified to extend its application to integrated enzymatic hydrolysis; it performed well when predicting 10-day cellulose hydrolysis at various experimental conditions. Comparison with the literature models showed that the modified HCH-1 model provided the best fit. Electronic supplementary material The online version of this article (10.1186/s13068-019-1371-5) contains supplementary material, which is available to authorized users.

The catalytic hydrolysis of cellulose allows the transformation of this sustainable and renewable raw material to obtain biofuels and high-added value chemicals. The process requires acidic catalysts, which should be preferably solid in order to make it greener and, thus, this work proposes the use of functionalized carbon materials for such an application. A mesoporous commercial carbon of trade name SA-30, abbreviated as SA in this work, has been chemically treated at room temperature to create acidic surface oxygen functional groups. The prepared carbon catalysts have been thoroughly characterized by N2 adsorption-desorption at − 196 ºC, temperature programmed desorption and X-ray photoelectron spectroscopy. SAS carbon (prepared by treatment with a saturated solution of (NH4)2S2O8 in 1 M H2SO4 and named by adding S to the name of the original carbon) is the most effective of the studied catalysts. It allows achieving high cellulose conversion (about 61%) and glucose selectivity. Thus, the low-cost functionalized carbons prepared at mild conditions are effective and promising catalysts for the transformation of cellulose into glucose. The authors thank Ministerio de Ciencia, Innovación y Universidades (RTI2018-095291-B-I00), GV/FEDER (PROMETEOII/2014/010) and University of Alicante (VIGROB-136) for financial support. F.-Z. Azar thanks the AECID (research scholarship for development (2015/2016)) and University of Alicante (cooperation programs for development) for financial support.

To enhance the cellulose hydrolysis at high solid loadings, an increased mixing intensity is generally required for the high solid loading hydrolysis, while it leads to higher energy consumption. In this study, the impact of mixing intensity on cellulose conversion during hydrolysis at different solid loadings were systematically studied. It was found that the increased mixing intensity is not necessary for more efficient cellulose hydrolysis. For cellulose hydrolysis at higher solid loadings, a lower mixing intensity is needed for a higher cellulose conversion. Although the increased mixing intensity promoted enzyme adsorption, it strengthened product inhibition and caused severer enzyme deactivation. Besides, mixing at the initial stage of cellulose hydrolysis was more crucial, while continuous mixing throughout the hydrolysis was not required for more efficient cellulose hydrolysis. Based on the mechanism study, a combined mixing strategy was developed to achieve efficient cellulose hydrolysis with about two-third reduction in energy consumption.

The enzymatic hydrolysis of cellulose and lignocellulosic materials is marked by a rate decrease along the reaction time. Cellobiohydrolase slow dissociation from the substrate and its inhibition by the cellobiose produced are relevant factors associated to the rate decrease. In that sense, addition of β-glucosidases to the enzyme cocktails employed in cellulose enzymatic hydrolysis not only produces glucose as final product but also reduces the cellobiohydrolase inhibition by cellobiose. The digestive β-glucosidase GH1 from the fall armyworm Spodoptera frugiperda, hereafter called Sfβgly, containing the mutation L428V showed an increased kcat for cellobiose hydrolysis. In comparison to assays conducted with the wild-type Sfβgly and cellobiohydrolase TrCel7A, the presence of the mutant L428V increased in 5 fold the initial rate of crystalline cellulose hydrolysis and reduced to one quarter the time needed to TrCel7A produce the maximum glucose yield. As our results show that mutant L428V complement the action of TrCel7A, the introduction of the equivalent replacement in β-glucosidases is a promising strategy to reduce costs in the enzymatic hydrolysis of lignocellulosic materials., Highlights • Mutation L428V increased the kcat for cellobiose of the β-glucosidase Sfβgly. • Sfβgly L428V enhanced the cellobiohydrolase TrCel7A activity upon cellulose. • Sfβgly L428V raised in 5 fold the initial rate of the cellulose hydrolysis. • Sfβgly L428V reduced to 1/4 the time needed for TrCel7A run out the substrate.

Mesostructured silica nanoparticles offer a unique opportunity in the field of biocatalysis thanks to their outstanding properties. The tunable pore size in the range of mesopores allows for immobilizing bulky enzyme molecules. The large surface area improves the catalytic efficiency by increasing enzyme loading and finely dispersing the biocatalyst molecules. The easily tunable pore morphology allows for creating a proper environment to host an enzyme. The confining effect of mesopores can improve the enzyme stability and its resistance to extreme pH and temperatures. Benefits also arise from other peculiarities of nanoparticles such as Brownian motion and easy dispersion. Fossil fuel depletion and environmental pollution have led to the need for alternative sustainable and renewable energy sources such as biofuels. In this context, lignocellulosic biomass has been considered as a strategic fuel source. Cellulases are a class of hydrolytic enzymes that convert cellulose into fermentable sugars. This review is intended to survey the immobilization of cellulolytic enzymes (cellulases and β-glucosidase) onto mesoporous silica nanoparticles and their catalytic performance, with the aim to give a contribution to the urgent action required against climate change and its impacts, by biorefineries’ development.

Nanocellulose has many applications in industrial sectors, such as in pulp and papermaking, production of synthetic textile fibers, dye, ink, and coating materials. The cellulose itself can be isolated from the waste of pine cone flower. This paper reports formic acid in the different concentrations (10%, 30%, and 60%) for hydrolyzing of cellulose using sonication technique (48 kHz) at 45 °C for 60 mins. The hydrolyzed cellulose was analyzed using FTIR and XRD spectrometry. It was found that the hydrolyzed-cellulose isolated was 92.4%, 94.6%, and 89.6%, respectively. The FTIR spectra provided the band for O-H (3435 cm−1) and C-O-C (1180-1060 cm−1) functional groups. However, the spectra also showed the C=C band for lignin impurities at 1661 cm−1. Furthermore, The XRD data gave similar 2-theta values for all hydrolyzed cellulose at 16°, 22°, and 34° respectively. The crystallite size was 18.34, 15.09, and 15.07 nm. Meanwhile, the crystallinity index was 50.50, 52.70, and 51.60% respectively.

Cellulases constitute an enzymatic complex involved in the cellulose hydrolysis β-1, 4-glycosidic linkages to release of glucose. Therefore, its application to degrade agro-industrial residues becomes relevant, since glucose is a product of industrial interest, aiming at its conversion into biocommodity production (e.g., enzymes, bioethanol and other value-added biochemicals). Thus, in natura Soybean hulls as well as fractions obtained from its alkaline, autohydrolysis and organosolv pretreatments were used as carbon sources in submerged fermentation processes to evaluate the cellulase-inducing capacity using a Penicillium sp. strain. Results showed an inductive effect on the production of 0.130 and 0.066 U/mL for CMCase and FPase, respectively, using 1% of the in natura residue. Regarding the fraction obtained from soybean hulls pretreated by autohydrolysis and organosolv, avicelase and β-Glucosidase displayed a production of 0.200 and 0.550 U/mL, respectively. Therefore, the use of pretreated Soybean hull revealed its potential as an alternative carbon source for the cellulase production, which may contribute significantly to biotechnological purposes by adding value to an agro-industrial residue.

Cellulose hydrolysis processes using concentrated acid usually involve two steps in order to obtain high glucose yields. The first step (pre-treatment) decrystallizes cellulose while the second step (post-hydrolysis) converts the amorphous cellulose to glucose. The two-step process developed by the Industrial Research Chair on Cellulosic Ethanol and Biocommodities and its industrial partner CRB Innovations Inc., includes an intermediate partial neutralization step, whose purpose is to decrease the amount of dilution water to be added for post-hydrolysis thus minimizing handling costs. In this work, the effect of several operating parameters on the glucose yield of this process was investigated using triticale cellulose and the best conditions yielding fermentable glucose (close to 100%) were determined. These conditions involve pre-treating cellulose at 30°C using 72 wt% H2SO4 with a H2SO4/dry cellulose mass ratio of 36 over 2 h, followed by a partial neutralization using 20 wt% NaOH at an H+/OH- molar ratio of 2.3-2.5 and a post-hydrolysis at 121°C for 10 min. HIGHLIGHTS Influence of operating parameters on the glucose yield have been investigated.Conditions for producing cellulosic glucose with yields close to 100% have been identified.

Beta-glucosidase (BGL) is a rate-limiting enzyme for cellulose hydrolysis as it acts in the final step of lignocellulosic biomass conversion to convert cellobiose into glucose, the final end product. Most of the fungal strains used for cellulase production are deficient in BGL hence BGL is supplemented into cellulases to have an efficient biomass conversion. Genetic engineering has enabled strain modification to produce BGL optimally with desired properties to be employed for biofuel applications. It has been cloned either directly into the host strains lacking BGL or into another expression system, to be overexpressed so as to be blended into BGL deficient cellulases. In this article, role of genetic engineering to overcome BGL limitations in the cellulase cocktail and its significance for biofuel applications has been critically reviewed. (C) 2017 Elsevier Ltd. All rights reserved.

[Background] New biorefinery concepts are necessary to drive industrial use of lignocellulose biomass components. Xylan recovery before enzymatic hydrolysis of the glucan component is a way to add value to the hemicellulose fraction, which can be used in papermaking, pharmaceutical, and food industries. Hemicellulose removal can also facilitate subsequent cellulolytic glucan hydrolysis., [Results] Sugarcane bagasse was pretreated with an alkaline-sulfite chemithermomechanical process to facilitate subsequent extraction of xylan by enzymatic or alkaline procedures. Alkaline extraction methods yielded 53% (w/w) xylan recovery. The enzymatic approach provided a limited yield of 22% (w/w) but produced the xylan with the lowest contamination with lignin and glucan components. All extracted xylans presented arabinosyl side groups and absence of acetylation. 2D-NMR data suggested the presence of O-methyl-glucuronic acid and p-coumarates only in enzymatically extracted xylan. Xylans isolated using the enzymatic approach resulted in products with molecular weights (Mw) lower than 6 kDa. Higher Mw values were detected in the alkali-isolated xylans. Alkaline extraction of xylan provided a glucan-enriched solid readily hydrolysable with low cellulase loads, generating hydrolysates with a high glucose/xylose ratio., [Conclusions] Hemicellulose removal before enzymatic hydrolysis of the cellulosic fraction proved to be an efficient manner to add value to sugarcane bagasse biorefining. Xylans with varied yield, purity, and structure can be obtained according to the extraction method. Enzymatic extraction procedures produce high-purity xylans at low yield, whereas alkaline extraction methods provided higher xylan yields with more lignin and glucan contamination. When xylan extraction is performed with alkaline methods, the residual glucan-enriched solid seems suitable for glucose production employing low cellulase loadings., This work was supported by FAPESP (Contract Numbers 08/56256-5 and 14/06923-6), CNPq, and CAPES. Daniela Sporck and Felipe Reinose thank CAPES for their student fellowships.

This review covers the topic of protein engineering of cellulases, mostly after 2009. Two major trends that are identified in this work are: first, the increased importance of results from computational protein engineering to drive ideas in the field, as experimental ideas and results often are still scarce, and, second, the further development of helper proteins for cellulose hydrolysis, such as lytic polysaccharide monooxygenase (LPO). The discussion in this work focuses both on improved attributes of cellulases and on the domains of cellulase that have been improved.